/*
 * Copyright 2018 The Cartographer Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef CARTOGRAPHER_MAPPING_2D_GRID_2D_H_
#define CARTOGRAPHER_MAPPING_2D_GRID_2D_H_

#include <vector>

#include "cartographer/mapping/2d/map_limits.h"
#include "cartographer/mapping/grid_interface.h"
#include "cartographer/mapping/probability_values.h"
#include "cartographer/mapping/proto/grid_2d.pb.h"
#include "cartographer/mapping/proto/submap_visualization.pb.h"
#include "cartographer/mapping/proto/submaps_options_2d.pb.h"
#include "cartographer/mapping/value_conversion_tables.h"

namespace cartographer {
	namespace mapping {

		proto::GridOptions2D CreateGridOptions2D(
			common::LuaParameterDictionary* const parameter_dictionary);

		enum class GridType { PROBABILITY_GRID, TSDF };

		class Grid2D : public GridInterface {
		public:
			Grid2D(const MapLimits& limits, float min_correspondence_cost,
				float max_correspondence_cost,
				ValueConversionTables* conversion_tables);
			explicit Grid2D(const proto::Grid2D& proto,
				ValueConversionTables* conversion_tables);

			// Returns the limits of this Grid2D.
			const MapLimits& limits() const { return limits_; }

			// Finishes the update sequence.
			void FinishUpdate();

			// Returns the correspondence cost of the cell with 'cell_index'.
			float GetCorrespondenceCost(const Eigen::Array2i& cell_index) const {
				if (!limits().Contains(cell_index)) return max_correspondence_cost_;
				return (*value_to_correspondence_cost_table_)
					[correspondence_cost_cells()[ToFlatIndex(cell_index)]];
			}

			virtual GridType GetGridType() const = 0;

			// Returns the minimum possible correspondence cost.
			float GetMinCorrespondenceCost() const { return min_correspondence_cost_; }

			// Returns the maximum possible correspondence cost.
			float GetMaxCorrespondenceCost() const { return max_correspondence_cost_; }

			// Returns true if the probability at the specified index is known.
			bool IsKnown(const Eigen::Array2i& cell_index) const {
				return limits_.Contains(cell_index) &&
					correspondence_cost_cells_[ToFlatIndex(cell_index)] !=
					kUnknownCorrespondenceValue;
			}

			// Fills in 'offset' and 'limits' to define a subregion of that contains all
			// known cells.
			void ComputeCroppedLimits(Eigen::Array2i* const offset,
				CellLimits* const limits) const;

			// Grows the map as necessary to include 'point'. This changes the meaning of
			// these coordinates going forward. This method must be called immediately
			// after 'FinishUpdate', before any calls to 'ApplyLookupTable'.
			virtual void GrowLimits(const Eigen::Vector2f& point);

			virtual std::unique_ptr<Grid2D> ComputeCroppedGrid() const = 0;

			virtual proto::Grid2D ToProto() const;

			virtual bool DrawToSubmapTexture(
				proto::SubmapQuery::Response::SubmapTexture* const texture,
				transform::Rigid3d local_pose) const = 0;

		protected:
			void GrowLimits(const Eigen::Vector2f& point,
				const std::vector<std::vector<uint16>*>& grids,
				const std::vector<uint16>& grids_unknown_cell_values);

			const std::vector<uint16>& correspondence_cost_cells() const {
				return correspondence_cost_cells_;
			}
			const std::vector<int>& update_indices() const { return update_indices_; }
			const Eigen::AlignedBox2i& known_cells_box() const {
				return known_cells_box_;
			}

			std::vector<uint16>* mutable_correspondence_cost_cells() {
				return &correspondence_cost_cells_;
			}

			std::vector<int>* mutable_update_indices() { return &update_indices_; }
			Eigen::AlignedBox2i* mutable_known_cells_box() { return &known_cells_box_; }

			// Converts a 'cell_index' into an index into 'cells_'.
			int ToFlatIndex(const Eigen::Array2i& cell_index) const {
				CHECK(limits_.Contains(cell_index)) << cell_index;
				return limits_.cell_limits().num_x_cells * cell_index.y() + cell_index.x();
			}

		private:
			MapLimits limits_;
			//记录各个栅格单元的空闲概率pfree，0表示对应栅格概率未知，[1, 32767]表示空闲概率，可通过
			//一对儿函数CorrespondenceCostToValue和ValueToCorrespondenceCost相互转换, 通过查表的方式
			//更新栅格单元的占用概率
			std::vector<uint16> correspondence_cost_cells_;
			float min_correspondence_cost_;//pfree的最小值
			float max_correspondence_cost_;//pfree的最大值
			std::vector<int> update_indices_;//记录更新过的栅格单元的存储索引

			// Bounding box of known cells to efficiently compute cropping limits.
			Eigen::AlignedBox2i known_cells_box_;
			const std::vector<float>* value_to_correspondence_cost_table_;
		};

	}  // namespace mapping
}  // namespace cartographer

#endif  // CARTOGRAPHER_MAPPING_2D_GRID_2D_H_
